Metabolomics is the study of cells by measuring profiles of all, or a large number, of their metabolites. Metabolomics was originally proposed as a method of functional genomics but its utility extends well beyond that - it is useful whenever an assessment of changes in metabolite levels is important. Metabolomics as a global approach is especially useful in identifying overall metabolic changes associated with breast cancer development and to identify most affected metabolites and metabolic networks. In this project the progression of malignancy of breast epithelial cells will be characterized under normal as well as oxidative stress conditions with detailed molecular profiles. Robust molecular signatures that uniquely characterize early stages of malignant transformation will be developed using mathematical, statistical, and machine learning algorithms. Fully malignant, intermediate and non-malignant breast epithelial cell cultures will be analyzed to obtain detailed molecular fingerprints. These fingerprints are processed with variable selection and discriminant analysis algorithms from which the determinant molecules for each stage of breast cancer development will be identified. To further increase the molecular detail of this approach, the cell cultures will be exposed to an oxidative stress caused by an appropriate concentration of cumene hydroperoxide, and subjected to the same data analysis workflow. The molecules identified as characteristic of each culture type, are important metabolic marker candidates for early stages of cancer development. At the same time they point to the molecular mechanisms of breast cancer origin and will increase our knowledge about the etiology of breast cancer.